Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $208.64   13.495%   $236.796   $236.80   $236.80   $236.80  
  Purchase #2 $129.62   7.519%   $139.3661   $139.37   $139.35   $139.40  
  Purchase #3 $105.62   11.741%   $118.0208   $118.02   $118.00   $118.00  
  Purchase #4 $174.55   5.685%   $184.4732   $184.47   $184.45   $184.50  
  Purchase #5 $211.91   6.842%   $226.4089   $226.41   $226.40   $226.40  
  Purchase #6 $35.93   3.365%   $37.139   $37.14   $37.15   $37.10  
  Purchase #7 $109.48   9.395%   $119.7656   $119.77   $119.75   $119.80  
  7 purchase totals = $975.75       $1,061.9696   $1,061.98   $1,061.90   $1,062.00